[Minios-devel] [UNIKRAFT PATCH v3 2/4] lib/ukswrand: Add seed generating function

[Vlad-Andrei BĂDOIU (78692) <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>]

This patch adds a new function, _get_random_seed32 for seed generaton. If the
pre-compiled config option is not selected, then rdrand is used on x86 and
ukplat_wall_clock on ARM.

Signed-off-by: Vlad-Andrei Badoiu <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>
---
 lib/ukswrand/Config.uk           | 22 +++++++++++++++++++---
 lib/ukswrand/include/uk/swrand.h |  2 ++
 lib/ukswrand/mwc.c               |  1 -
 lib/ukswrand/swrand.c            | 22 +++++++++++++++++++++-
 4 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/lib/ukswrand/Config.uk b/lib/ukswrand/Config.uk
index c58371bb..e056b4c5 100644
--- a/lib/ukswrand/Config.uk
+++ b/lib/ukswrand/Config.uk
@@ -14,9 +14,25 @@ config LIBUKSWRAND_MWC
                Use multiply-with-carry algorithm
 endchoice
 
-config LIBUKSWRAND_INITIALSEED
-       int "Initial random seed"
-       default 23
+choice
+    prompt "Initial seed"
+    default LIBUKSWRANDR_INITIALSEED_TIME
+
+config LIBUKSWRAND_INITIALSEED_TIME
+    bool "Platform timestamp"
+
+config LIBUKSWRAND_INITIALSEED_RDRAND
+    depends on ARCH_X86_64 && (MARCH_X86_64_COREI7AVXI)
+    bool "`rdrand` instruction"
+
+config LIBUKSWRAND_INITIALSEED_USECONSTANT
+    bool "Compiled-in constant"
+endchoice
+
+config LIBUKSWRAND_INITIALSEED_CONSTANT
+    int "Initial seed constant"
+    depends on LIBUKSWRAND_INITIALSEED_USECONSTANT
+    default 23
 
 config LIBUKSWRAND_DEVFS
        bool "Register random and urandom device to devfs"
diff --git a/lib/ukswrand/include/uk/swrand.h b/lib/ukswrand/include/uk/swrand.h
index 35f3e2fe..7f5eeed2 100644
--- a/lib/ukswrand/include/uk/swrand.h
+++ b/lib/ukswrand/include/uk/swrand.h
@@ -39,6 +39,7 @@
 #include <uk/arch/types.h>
 #include <uk/plat/lcpu.h>
 #include <uk/config.h>
+#include <uk/plat/time.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -51,6 +52,7 @@ extern struct uk_swrand uk_swrand_def;
 void uk_swrand_init_r(struct uk_swrand *r, __u32 seed);
 __u32 uk_swrand_randr_r(struct uk_swrand *r);
 
+__u32 _get_random_seed32(void);
 /* Uses the pre-initialized default generator  */
 /* TODO: Add assertion when we can test if we are in interrupt context */
 /* TODO: Revisit with multi-CPU support */
diff --git a/lib/ukswrand/mwc.c b/lib/ukswrand/mwc.c
index 3ee07051..19166c4b 100644
--- a/lib/ukswrand/mwc.c
+++ b/lib/ukswrand/mwc.c
@@ -93,4 +93,3 @@ __u32 uk_swrand_randr_r(struct uk_swrand *r)
        r->c = c;
        return (r->Q[i] = y - x);
 }
-
diff --git a/lib/ukswrand/swrand.c b/lib/ukswrand/swrand.c
index d9497bf8..16ad3496 100644
--- a/lib/ukswrand/swrand.c
+++ b/lib/ukswrand/swrand.c
@@ -37,6 +37,26 @@
 
 #define UK_SWRAND_CTOR_PRIO    1
 
+__u32 _get_random_seed32(void)
+{
+       __u32 val;
+
+#ifdef CONFIG_LIBUKSWRAND_INITIALSEED_TIME
+       val = (__u32)ukplat_wall_clock();
+#endif
+
+#ifdef CONFIG_LIBUKSWRAND_INITIALSEED_RDRAND
+       asm volatile ("rdrand %%eax;"
+               : "=a" (val));
+#endif
+
+#ifdef CONFIG_LIBUKSWRAND_INITIALSEED_USECONSTANT
+       val = CONFIG_LIBUKSWRAND_INITIALSEED_CONSTANT;
+#endif
+
+       return val;
+}
+
 ssize_t uk_swrand_fill_buffer(void *buf, size_t buflen)
 {
        size_t step, chunk_size, i;
@@ -60,7 +80,7 @@ ssize_t uk_swrand_fill_buffer(void *buf, size_t buflen)
 static void _uk_swrand_ctor(void)
 {
        uk_pr_info("Initialize random number generator...\n");
-       uk_swrand_init_r(&uk_swrand_def, CONFIG_LIBUKSWRAND_INITIALSEED);
+       uk_swrand_init_r(&uk_swrand_def, _get_random_seed32());
 }
 
 UK_CTOR_FUNC(UK_SWRAND_CTOR_PRIO, _uk_swrand_ctor);
-- 
2.20.1


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